1. Field of the Invention
The present invention relates to a head lamp device for a motor vehicle.
2. Description of Background Art
A two-bulb head lamp device for a motor vehicle is set forth in the present inventor's co-pending Japanese Laid-open Patent Publication No. 5-85435. The proposed head lamp device comprises two bulbs and a pair of reflecting mirrors which are accommodated in one housing. Water vapor in the housing is evaporated by the heat of the bulbs and tends to be attached to the inner surface of a lens, thereby frosting the lens. Head lamp devices designed to solve this problem have an opening defined in the housing for discharging heat and water vapor out of the housing.
A head lamp device for a motor vehicle as disclosed in FIG. 3 of Japanese Laid-open Utility Model Publication No. 4-135105 has a J-shaped vent pipe (460) disposed on the back of a housing for discharging heat or the like. The optical axis can be adjusted vertically by rotating an optical axis adjusting mechanism 5A shown in FIG. 3. Generally, head lamp devices have an optical axis adjusting mechanism. An optical axis adjustment will hereinafter be referred to as "aiming" and an optical axis adjusting mechanism as the "aiming mechanism."
An aiming rod or aiming bolt, corresponding to the component 50A in FIG. 3 of Japanese Laid-open Utility Model Publication No. 4-135105, is considerably long. If the aiming rod was short, then a tool for turning the aiming rod would interfere with the J-shaped vent pipe, and would damage or dismount the J-shaped vent pipe when operated in error. Therefore, the aiming rod is of a sufficient length. The long aiming rod, however, requires a space behind the head lamp, and such a space is not preferable from the standpoint of positioning devices in a compact arrangement.